Semiconductor device and manufacturing method thereof

ABSTRACT

A semiconductor device with high reliability is provided in which an insulating property of an insulating layer is high and connection failure is prevented.  
     The semiconductor device includes: a silicon substrate; a low-temperature aluminum film formed on silicon substrate and including a polycrystal; and a high-temperature aluminum film. An opening is formed in a surface of a high-temperature aluminum film by a crystal grain boundary. A distance between side walls of the opening becomes small as closer to silicon substrate.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to semiconductor devices andmanufacturing methods thereof, and more particularly to a semiconductordevice having a conductive layer as an interconnection layer and amanufacturing method thereof.

[0003] 2. Description of the Background Art

[0004] Conventionally, aluminum is used for an interconnection layer ofa semiconductor device. The problem related to a method of manufacturingthe interconnection with aluminum will be described.

[0005] FIGS. 18 to 22 are cross sectional views shown in conjunctionwith the problem associated with the conventional manufacturing method.

[0006] Referring to FIG. 18, an interlayer insulating film 102 is formedon a silicon substrate 101. A titanium nitride film 103 as a barrierlayer is formed on interlayer insulating film 102. An aluminum film(hereinafter referred to as a high-temperature aluminum film) 105 isformed on titanium nitride film 103 by sputtering at a high temperatureof about 400° C.

[0007] The formation of the aluminum film at such high temperatureincreases planarity of high-temperature aluminum film 105. A crystalgrain size of high-temperature aluminum film 105 is larger than that ofan aluminum film formed at a low temperature. Therefore, whenhigh-temperature aluminum film 105 is cooled, a recess 106 is formed bythe grain boundary, for example, due to shrinkage of a crystal.

[0008] Referring to FIG. 19, an anti-reflection film 109 of titaniumnitride is formed on a surface of high-temperature aluminum film 105. Atthe time, a thickness of anti-reflection film 109 is particularly smallat a corner 106 a of recess 106.

[0009] Referring to FIG. 20, resist is applied onto anti-reflection film109. After the resist is exposed to light, a resist pattern 110 isformed by development using developer. As the thickness ofanti-reflection film 109 is small at corner 106 a of recess 106, thedeveloper melts a portion of anti-reflection film 109 and also a portionof high-temperature aluminum film 105. Thus, recess 106 extends and anopening 107 is formed. Opening 107 is greater than the opening atanti-reflection film 109.

[0010] Referring to FIG. 21, etching of anti-reflection film 109 andhigh-temperature aluminum film 105 is started using resist pattern 110as a mask. At the time, etch residue 111, formed by reaction ofhigh-temperature aluminum film 105 and etchant, is left at a portioncovered by anti-reflection film 109 in opening 107. It is relativelydifficult to etch etching residue 111.

[0011] Referring to FIG. 22, when etching is further performed, etchresidue 111 acts as a mask to leave high-temperature aluminum film 105and titanium nitride film 103 thereunder. As a result, interconnectionlayers 112 and 113 are formed and, at the same time, residues 121 and122 including conductive portions are formed at portions which wouldhave essentially been free of such conductive materials.

[0012] Formation of an interlayer insulating film on residues 121 and122 would result in insulation failure of the interlayer insulating filmand reduction in reliability of the semiconductor device.

SUMMARY OF THE INVENTION

[0013] The present invention is made to solve the aforementionedproblem. An object according to one aspect of the present invention isto provide a semiconductor device provided with high reliability andpreventing insulation failure.

[0014] An object according to another aspect of the present invention isto provide a semiconductor device provided with high adhesion with alower layer and preventing connection failure.

[0015] The semiconductor device according to one aspect of the presentinvention includes a semiconductor substrate and a conductive layerincluding polycrystal formed on the semiconductor substrate. A recess isformed by a grain boundary in a surface of the conductive layer. Adistance between side walls of the recess becomes small as closer to thesemiconductor substrate.

[0016] In the semiconductor device having such structure, as thedistance between the side walls of the recess becomes small as closer tothe semiconductor substrate, there would be no space for the residuecaused by the etching in the recess in the conductive layer and anyconductive material is not left at the unexpected portion. As a result,the semiconductor device provided with high reliability and preventinginsulation failure is provided.

[0017] More preferably, the conductive layer includes first and secondconductive layers. The first conductive layer is formed on thesemiconductor substrate and includes a polycrystal having a firstaverage grain size. The second conductive layer is formed with a recesson the first conductive layer and includes a polycrystal having a secondaverage grain size which is greater than the first average grain size.

[0018] As the first average grain size is relatively small as comparedwith the second average grain size, adhesion between the firstconductive layer of the first average grain size and a lower layerincreases. Thus, the semiconductor device provided with high reliabilityand preventing connection failure is provided.

[0019] More preferably, the semiconductor device further includes a thinfilm layer formed on the conductive layer and having a material which isdifferent from that of the conductive layer.

[0020] More preferably, the thin film layer includes titanium or siliconnitride. Then, the thin film layer can be used as a barrier layer oranti-reflection layer.

[0021] More preferably, the conductive layer includes aluminum.

[0022] More preferably, the semiconductor device further includes aninsulating layer formed on the semiconductor substrate and a barrierlayer formed on the insulating layer. The conductive layer is formed onthe barrier layer.

[0023] Then, as the barrier layer is formed under the conductive layer,diffusion of atoms of the conductive layer can be prevented.

[0024] A semiconductor device according to another aspect of the presentinvention includes first, second and third conductive layers. The firstconductive layer is formed on the semiconductor substrate and includes apolycrystal having a first average grain size. The second conductivelayer is formed on the first conductive layer and includes a polycrystalhaving a second average grain size which is greater than the firstaverage grain size. The third conductive layer is formed on the secondconductive layer and includes a polycrystal having a third average grainsize which is smaller than the second average grain size.

[0025] In the semiconductor device having such structure, as the averagegrain size of the third conductive layer formed on the second conductivelayer is small, formation of a recess by a grain boundary in the thirdconductive layer is prevented. As there would be no space for residuecaused by etching in the third conductive layer, a conductive materialis not left at an unexpected portion. As a result, the semiconductordevice provided with high reliability and preventing insulation failureis provided.

[0026] As a first average grain size of the first conductive layerformed on the semiconductor substrate is relatively small, adhesion witha lower layer is increased and connection failure can be prevented.

[0027] More preferably, a recess is formed in a surface of the secondconductive layer by the grain boundary. A distance between side walls ofthe recess becomes small as closer to the semiconductor substrate.

[0028] Then, there would be no space for the residue caused by theetching in the third conductive layer covering the recess. As a result,the conductive material is not left at the unexpected portion, so thatreliability of the semiconductor device is further increased.

[0029] More preferably, the semiconductor device further includes a thinfilm layer formed on the third conductive layer and having a materialwhich is different from that of the third conductive layer.

[0030] More preferably, the thin film layer includes titanium or siliconnitride. Then, the thin film layer can be used as an anti-reflectionfilm or barrier layer.

[0031] More preferably, the conductive layer includes aluminum.

[0032] More preferably, the semiconductor device includes an insulatinglayer formed on the semiconductor substrate and a barrier layer formedon the insulating layer. The conductive layer is formed on the barrierlayer.

[0033] Then, as the barrier layer is formed under the conductive layer,diffusion of atoms of the conductive layer can be prevented.

[0034] A method of manufacturing a semiconductor device according to oneaspect of the present invention includes a step of forming a conductivelayer including a polycrystal on a semiconductor substrate. Theconductive layer having a recess in its surface formed by a grainboundary. A distance between side walls of the recess becomes large ascloser to the semiconductor substrate. The method of manufacturing thesemiconductor device includes a step of forming the side walls such thata distance therebetween becomes small as closer to the semiconductorsubstrate.

[0035] In the method of manufacturing the semiconductor device havingsuch structure, the side walls prevents formation of a space for theresidue in the conductive layer. Thus, a conductive material is not leftat an unexpected portion, so that the semiconductor device provided withhigh reliability and preventing insulation failure is provided.

[0036] More preferably, the step of forming the conductive layerincludes a step of forming a first conductive layer at a firsttemperature on the semiconductor substrate, and a step of forming asecond conductive layer having a recess at a second temperature which ishigher than the first temperature on the first conductive layer.

[0037] As the first conductive layer is formed at the relatively lowtemperature, adhesion between the first conductive layer and a lowerlayer increases. As a result, the semiconductor device provided withhigh reliability and preventing connection failure is provided.

[0038] More preferably, the step of forming the second conductive layerincludes a step of keeping the second conductive layer in the atmosphereat the second temperature after the second conductive layer is formed bysputtering at a temperature which is lower than the second temperature.

[0039] More preferably, the method of manufacturing the semiconductordevice further includes a step of forming a thin film layer having amaterial which is different from that of the conductive layer on theconductive layer having the formed side walls.

[0040] More preferably, the method of manufacturing the semiconductordevice further includes a step of forming an insulating layer on thesemiconductor substrate and a step of forming a barrier layer on theinsulating layer. The step of forming the conductive layer includes astep of forming a conductive layer on the barrier layer.

[0041] Then, as the barrier layer is formed under the conductive layer,diffusion of atoms of the conductive layer is prevented.

[0042] More preferably, the step of forming the side walls includes astep of sputter etching the conductive layer.

[0043] A method of manufacturing a semiconductor device according toanother aspect of the present invention includes a step of forming afirst conductive layer on a semiconductor substrate at a firsttemperature, a step of forming a second conductive layer on the firstconductive layer at a second temperature higher than the firsttemperature, and a step of forming a third conductive layer on thesecond conductive layer at a third temperature lower than the secondtemperature.

[0044] In the method of manufacturing the semiconductor device havingsuch structure, as the third conductive layer is formed at therelatively low temperature, formation of a recess in a surface of thethird conductive layer by a grain boundary is prevented. Thus, therewould be no space for a residue caused by the etching in the surface ofthe third conductive layer. As a result, any conductive material is notleft at an unexpected portion, so that the semiconductor device providedwith high reliability and preventing insulation failure is provided.

[0045] As the first conductive layer is formed at the relatively lowtemperature, adhesion with a lower layer increases. Thus, thesemiconductor device provided with high reliability and preventingconnection failure is provided.

[0046] Preferably, the step of forming the second conductive layerincludes a step of forming a second conductive layer having in itssurface a recess caused by the grain boundary, where a distance betweenside walls of the recess becomes large as closer to the semiconductorsubstrate. The method of manufacturing the semiconductor device furtherincludes a step of forming the side walls such that the distancetherebetween becomes small as closer to the semiconductor substrate. Thestep of forming the third conductive layer includes a step of formingthe third conductive layer on the second conductive layer having theformed side walls.

[0047] As the side walls of the recess are thus formed, even when thethird conductive layer is formed thereon, there would be no space forthe residue caused by the etching in the third conductive layer. As aresult, any conductive material is not left at the unexpected portion,so that the semiconductor device provided with higher reliability andpreventing insulating failure is provided.

[0048] More preferably, the step of forming the side walls includes astep of sputter etching the conductive layer.

[0049] More preferably, the method of manufacturing the semiconductordevice further includes a step of forming a thin film layer having amaterial which is different from that of the third conductive layer onthe third conductive layer.

[0050] The step of forming the second conductive layer includes a stepof keeping the second conductive layer in the atmosphere at the secondtemperature after the second conductive layer is formed by sputtering ata temperature lower than the second temperature.

[0051] More preferably, the method of manufacturing the semiconductordevice further includes a step of forming an insulating layer on thesemiconductor substrate and a step of forming a barrier layer on theinsulating layer. The step of forming the conductive layer includes astep of forming a conductive layer on the barrier layer. Then, as theconductive layer is formed on the barter layer, diffusion of atoms ofthe conductive layer is prevented.

[0052] The foregoing and other objects, features, aspects and advantagesof the present invention will become more apparent from the followingdetailed description of the present invention when taken in conjunctionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0053]FIG. 1A is a schematic cross sectional view showing asemiconductor device according to a first embodiment of the presentinvention, and FIG. 1B is a partial cross sectional view showing inenlargement an opening in the semiconductor device according to thefirst embodiment of the present invention.

[0054]FIG. 2 is a cross sectional view showing a first step of a methodof manufacturing the semiconductor device shown in FIG. 1.

[0055]FIG. 3 is a partial cross sectional view showing in enlargement arecess of the semiconductor device shown in FIG. 2.

[0056] FIGS. 4 to 7 are cross sectional views showing second to fifthsteps of the method of manufacturing the semiconductor device shown inFIG. 1.

[0057]FIG. 8 is a cross sectional view showing a semiconductor deviceaccording to a second embodiment of the present invention.

[0058] FIGS. 9 to 12 are cross sectional views showing first to fourthsteps of a method of manufacturing the semiconductor device shown inFIG. 8.

[0059]FIG. 13 is a cross sectional view showing a semiconductor deviceaccording to a third embodiment of the present invention.

[0060] FIGS. 14 to 17 are cross sectional views showing first to fourthsteps of a method of manufacturing the semiconductor device shown inFIG. 13.

[0061] FIGS. 18 to 22 are cross sectional views showing first to fifthsteps of a method of manufacturing a conventional semiconductor device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0062] Embodiments of the present invention will now be described withreference to the drawings.

[0063] First Embodiment

[0064] Referring to FIG. 1A, in a semiconductor device according to thepresent invention, an interlayer insulating film 2 is formed on asilicon substrate 1 as a semiconductor substrate. An interconnectionlayer 12 is formed on interlayer insulating film 2. Interconnectionlayer 12 includes: a titanium nitride film 3 as a barrier layer; alow-temperature aluminum layer (an aluminum layer formed at a lowtemperature) 4 as a first conductive layer; a high-temperature aluminumlayer 5 as a second conductive layer; and an anti-reflection film 9 as athin film layer having two layers of titanium and titanium nitride.

[0065] Titanium nitride film 3 has a thickness of about 100 nm. Athickness of low-temperature aluminum film 4 including polycrystallinealuminum is about 150 nm and has an average crystal grain size of about0.5 μm. High-temperature aluminum film 5 is formed on low-temperaturealuminum film 4. A thickness of high-temperature aluminum film is about200 nm. High-temperature aluminum film 5 includes polycrystallinealuminum and has an average crystal grain size of about 1.5 μm. Anopening 107 is formed as a recess in a surface of high-temperaturealuminum film 5.

[0066] Referring to FIG. 1B, opening 7 is defined by grain boundaries ofcrystals 5 a to 5 c of aluminum. Opening 7 has a depth D of 20 nm, adiameter W₁ at its upper portion of about 50 nm and a diameter W₂ at itsbottom portion of 30 nm. A distance between side walls 7 a and 7 b ofopening 7 becomes small as closer to silicon substrate 1.

[0067] Now, a method of manufacturing the semiconductor device shown inFIG. 1 will be described. Referring to FIG. 2, an interlayer insulatingfilm 2 is formed by CVD (Chemical Vapor Deposition) on a surface ofsilicon substrate 1. A titanium nitride film 3 is formed on interlayerinsulating film 2 by PVD Physical Vapor Deposition).

[0068] A low-temperature aluminum film 4 is formed on titanium nitridefilm 3 by sputtering at a low temperature of about 100° C.High-temperature aluminum film 5 is formed on low-temperature aluminumfilm 4 by sputtering at a high temperature of about 400° C. Thereafter,high-temperature aluminum film 5 is cooled, and a recess 6 is formed ina surface thereof by crystal depression.

[0069] Referring to FIG. 3, recess 6 is formed by grain boundaries ofcrystals 5 a to 5 c of aluminum, that is, crystal grain boundaries ofaluminum. Recess 6 is formed by depression of crystal 5 b of aluminum.

[0070] Returning to FIG. 2, the largest portion of recess 6 has adiameter W₂, and a diameter at the surface of high-temperature aluminumfilm 5 is W₃ (20 nm). A distance between side walls 6 a and 6 b ofrecess 6 becomes small as closer to silicon substrate 1.

[0071] Referring to FIG. 4, the surface of high-temperature aluminumfilm 5 is sputter etched using argon gas. Thus, opening 7 is formed byprocessing the side walls of recess 6. A distance between side walls 7 aand 7 b of opening 7 becomes small as doser to silicon substrate 1. Acorner 7 c of opening 7 is arcuate in shape.

[0072] Referring to FIG. 5, an anti-reflection film 9 having two layersof titanium and titanium nitride is formed by PVD to coverhigh-temperature aluminum film 5.

[0073] Referring to FIG. 6, resist is applied onto anti-reflection film9. After the resist is exposed to light, it is developed by developer toform a resist pattern 10.

[0074] Referring to FIG. 7, anti-reflection film 9, high-temperaturealuminum film 5, low-temperature aluminum film 4 and titanium nitridefilm 3 are etched in accordance with resist pattern 10. Thus, aninterconnection layer 12 is formed. Thereafter, resist pattern 10 isremoved to complete the semiconductor device shown in FIG. 1.

[0075] According to the semiconductor device and manufacturing methodthereof, first, side walls 7 a and 7 b of opening 7 are formed as shownin FIG. 4. As anti-reflection film 9 is formed over opening 7, anyparticular portion of anti-reflection film 9 would not have extremelysmall thickness. Thus, if the resist is developed in the step shown inFIG. 6, formation of a space for etch residue is prevented. As a result,etching in accordance with resist pattern 10 ensures that a conductivematerial is left exclusively under resist pattern 10 and the otherportion would be free of the conductive material. Therefore, thesemiconductor device is provided with higher reliability.

[0076] Low-temperature aluminum film 4 is formed on titanium nitridefilm 3. As low-temperature aluminum film 4 is provided with highadhesion with other layers, the semiconductor device provided with highreliability and preventing connection failure is achieved.

[0077] Second Embodiment

[0078] Referring to FIG. 8, silicon substrate 1, interlayer insulatingfilm 2, titanium nitride film 3 and low-temperature aluminum film 4 arethe same as those of the first embodiment.

[0079] A high-temperature aluminum-film 5 is formed on low-temperaturealuminum film 4. High-temperature aluminum film 5 has an average grainsize of 1.5 μm and a thickness of 200 nm. A recess 6 is formed in asurface of high-temperature aluminum film 5. A dimension of recess 6 isthe same as that shown in FIG. 2.

[0080] Low-temperature aluminum film 21 is formed over recess 6.Low-temperature aluminum film 21 has a thickness of 100 nm and anaverage grain size of 0.1 μm. A distance between side walls 6 a and 6 bof recess 6 becomes small as closer to silicon substrate 1. Ananti-reflection film 22 having two layers of titanium and titaniumnitride is formed on low-temperature aluminum film 21.

[0081] Now, a method of manufacturing the semiconductor device shown inFIG. 8 will be described. Referring to FIG. 9, as in the firstembodiment, an interlayer insulating film 2, titanium nitride film 3,low-temperature aluminum film 4 and high-temperature aluminum film 5 areformed on silicon substrate 1. Recess 6 is formed in the surface ofhigh-temperature aluminum film 5.

[0082] Referring to FIG. 10, low-temperature aluminum film 21 is formedby sputtering at a temperature of about 100° C. An anti-reflection film22 is formed on low-temperature aluminum film 21 by PVD.

[0083] Referring to FIG. 11, resist is applied onto anti-reflection film22. After the resist is exposed to light, it is developed by a developerto form a resist pattern 23.

[0084] Referring to FIG. 12, anti-reflection film 22, low-temperaturealuminum film 21, high-temperature aluminum film 5, low-temperaturealuminum film 4 and titanium nitride film 3 are etched in accordancewith resist pattern 23. Thus, an interconnection layer 25 is formed.Thereafter, resist pattern 23 is removed to complete the semiconductordevice shown in FIG. 8.

[0085] According to the semiconductor device and manufacturing methodthereof, low-temperature aluminum film 21 is formed in recess 6. As theaverage grain size of low-temperature aluminum film 21 is relativelysmall, it is unlikely that depression of a crystal is caused. Thus, evenwhen anti-reflection film 22 is formed on low-temperature aluminum film21, any portion of anti-reflection film 22 would not have a smallerthickness. Therefore, low-temperature aluminum film 21 would not beetched at the time of development of resist pattern 23, and there is notany space for the etch residue. In addition, insulation failure isprevented. As shown in FIG. 12, the conductive material is leftexclusively under resist pattern 23, and the other portion would be freeof conductive material. As a result, the semiconductor device with highreliability is achieved.

[0086] Low-temperature aluminum film 4 is formed on titanium nitridefilm 3. As low-temperature aluminum film 4 has high adhesion with otherlayers, connection failure is prevented. As a result, the semiconductordevice with high reliability is achieved.

[0087] Third Embodiment

[0088] Referring to FIG. 13, an interlayer insulating film 2, titaniumnitride film 3, low-temperature aluminum film 4 and high-temperaturealuminum film 5 are formed on a silicon substrate 1. An opening 7 isformed in a surface of high-temperature aluminum film 5, and a distancebetween side walls 7 a and 7 b of opening 7 becomes small at closer tosilicon substrate 1. Low-temperature aluminum film 31 is formed inopening 7.

[0089] An anti-reflection film 32 having two layers of titanium andtitanium nitride is formed on low-temperature aluminum film 31. Titaniumnitride film 3, low-temperature aluminum film 4, high-temperaturealuminum film 5, low-temperature aluminum film 31 and anti-reflectionfilm 32 comprise an interconnection layer 35.

[0090] Now, a method of manufacturing the semiconductor device shown inFIG. 13 will be described. Referring to FIG. 14, as in the steps shownin FIGS. 2 and 4 of the first embodiment, interlayer insulating film 2,titanium nitride film 3, low-temperature aluminum film 4 andhigh-temperature aluminum film 5 are formed on silicon substrate 1.Opening 7 is formed by sputter etching the surface of high-temperaturealuminum film 5 by argon. The distance between side walls 7 a and 7 b ofopening 7 becomes small as closer to silicon substrate 1.

[0091] Referring to FIG. 15, low-temperature aluminum film 31 is formedto cover opening 7 by sputtering at a temperature of about 100° C.Anti-reflection film 32 having two layers of titanium and titaniumnitride is formed on low-temperature aluminum film 31 by CVD.

[0092] Referring to FIG. 16, resist is applied onto anti-reflection film32. After the resist is exposed to light, it is developed by developer.Thus, a resist pattern 33 is formed.

[0093] Referring to FIG. 17, anti-reflection film 32, low-temperaturealuminum film 31, high-temperature aluminum film 5, low-temperaturealuminum film 4 and titanium nitride film 3 are etched in accordancewith resist pattern 33 to form an interconnection layer 35. Thereafter,resist pattern 33 is removed to complete the semiconductor device shownin FIG. 13.

[0094] According to the semiconductor device and manufacturing methodthereof, first, low-temperature aluminum film 31 is formed onhigh-temperature aluminum film 5 at a low temperature as shown in FIG.15. As a crystal grain size of low-temperature aluminum film 31 isrelatively small, it is unlikely that a recess is formed inlow-temperature aluminum film 31. Recess 6 in the high-temperaturealuminum film is processed to be tapered opening 7, so that a surface oflow-temperature aluminum film 31 is almost planar. Accordingly, evenwhen anti-reflection film 32 is formed on low-temperature aluminum film31, any portion of anti-reflection film 32 would not have a smallerthickness. Therefore, low-temperature aluminum film 31 is not etched atthe time of development of resist pattern 33, whereby formation of aspace for the etch residue is prevented. As a result, a conductivematerial is left exclusively under resist pattern 33 and the otherportions are substantially flee of the conductive material, as shown inFIG. 12. Therefore, the semiconductor device provided with highreliability and preventing connection failure is achieved.

[0095] As high-temperature aluminum film 4 with high adhesion with othermaterial is formed on titanium nitride film 3, semiconductor device withhigh reliability and preventing connection failure is achieved.

[0096] Although the embodiments of the present invention have beendescribed above, various modifications can be made to the embodiments.For example, in the above sputtering at the high temperature has beenexemplified as a method of forming high-temperature aluminum film 5.However, the method is not limited to this and, for example, a so-calledhigh temperature reflow method may be used in which an aluminum film isformed by sputtering at a low temperature of about 100° C. and thealuminum film is kept at a high temperature of about 400° C.

[0097] Although anti-reflection film 9 has been described as having twolayers of titanium and titanium nitride, a silicon nitride film may beused as the anti-reflection film. Further, though aluminum has beendescribed as the conductive material of the interconnection layer,copper or tungsten may be employed.

[0098] In some cases, a boundary between low temperature having aluminumfilm 4 and high-temperature aluminum film 5 is not clearly defined.Then, a portion of low-temperature aluminum film 4 that is closer totitanium nitride film 3 has a relatively small grain size, whereas theportion closer to high temperature having aluminum film 5 has arelatively large grain size.

[0099] Although the present invention has been described and illustratedin detail, it is clearly understood that the same is by way ofillustration and example only and is not to be taken by way oflimitation, the spirit and scope of the present invention being limitedonly by the terms of the appended claims.

What is claimed is:
 1. A semiconductor device, comprising: asemiconductor substrate; and a conductive layer formed on saidsemiconductor substrate and including polycrystals, said conductivelayer including in its surface a recess caused by a crystal grainboundary and having side walls formed such that a distance therebetweenbecomes small as closer to said semiconductor substrate.
 2. Thesemiconductor device according to claim 1 , wherein said conductivelayer includes: a first conductive layer formed on said semiconductorsubstrate and including a polycrystal having a first average grain size;and a second conductive layer formed on said first conductive layer,including a polycrystal having a second average grain size greater thansaid first average grain size and having said recess.
 3. Thesemiconductor device according to claim 1 , further comprising a thinfilm layer formed on said conductive layer and having a materialdifferent from that of said conductive layer.
 4. The semiconductordevice according to claim 1 , wherein said conductive layer includesaluminum.
 5. The semiconductor device according to claim 1 , furthercomprising an insulating layer formed on said semiconductor substrateand a barrier layer formed on said insulating layer, said conductivelayer being formed on said barrier layer.
 6. A semiconductor device,comprising: a first conductive layer formed on a semiconductor substrateand including a polycrystal having a first average grain size; a secondconductive layer formed on said first conductive layer and including apolycrystal having a second average grain size greater than said firstaverage grain size; and a third conductive layer formed on said secondconductive layer and including a polycrystal having a third averagegrain size smaller than said second average grain size.
 7. Thesemiconductor device according to claim 6 , wherein a recess is formedin a surface of said second conductive layer by a crystal grainboundary, and a distance between side walls of said recess becomes smallas closer to said semiconductor substrate.
 8. The semiconductor deviceaccording to claim 6 , further comprising a thin film layer formed onsaid third conductive layer and having a material different from thatsaid third conductive layer.
 9. The semiconductor device according toclaim 6 , wherein said conductive layer includes aluminum.
 10. Thesemiconductor device according to claim 6 , further comprising aninsulating layer formed on said semiconductor substrate and a barrierlayer formed on said insulating layer, said conductive layer beingformed on said barrier layer.
 11. A method of manufacturing asemiconductor device, comprising the steps of: forming a conductivelayer including a polycrystal on a semiconductor substrate, saidconductive layer having a recess in its surface formed by a crystalgrain boundary, a distance between side walls of said recess becominglarge as closer to said semiconductor substrate; and processing saidside walls of said recess such that the distance therebetween becomessmall as closer to said semiconductor substrate.
 12. The method ofmanufacturing the semiconductor device according to claim 11 , whereinsaid step of forming said conductive layer includes the steps of:forming a first conductive layer on said semiconductor substrate at afirst temperature; and forming a second conductive layer having saidrecess on said first conductive layer at a second temperature higherthan said first temperature.
 13. The method of manufacturing thesemiconductor device according to claim 11 , further comprising the stepof forming a thin film layer having a material different from that ofsaid conductive layer on said conductive layer having the processed sidewalls.
 14. The method of manufacturing the semiconductor deviceaccording to claim 11 , further comprising the step of forming aninsulating layer on said semiconductor substrate and the step of forminga barrier layer on said insulating layer, said step of forming saidconductive layer including the step of forming said conductive layer onsaid barrier layer.
 15. The method of manufacturing the semiconductordevice according to claim 11 , wherein said step of processing said sidewalls includes the step of sputter etching said conductive layer.
 16. Amethod of manufacturing a semiconductor device, comprising the steps of:forming a first conductive layer on a semiconductor substrate at a firsttemperature; forming a second conductive layer on said first conductivelayer at a second temperature higher than said first temperature; andforming a third conductive layer on said second conductive layer at athird temperature lower than said second temperature.
 17. The method ofmanufacturing the semiconductor device according to claim 16 , whereinsaid step of forming said second conductive layer includes the step offorming said second conductive layer with a recess formed in its surfaceby a crystal grain boundary and having side walls, a distance betweensaid side walls becoming large as closer to said semiconductorsubstrate, said method further comprising the step of processing saidside walls such that a distance therebetween becomes small as closer tosaid semiconductor substrate, and wherein said step of forming saidthird conductive layer includes the step of forming said thirdconductive layer on said second conductive layer having said processedside walls.
 18. The method of manufacturing the semiconductor deviceaccording to claim 16 , wherein said step of processing said side wallsfurther includes the step of sputter etching said conductive layer. 19.The method of manufacturing the semiconductor device according to claim16 , further comprising the step of forming a thin film layer having amaterial different from that of said third conductive layer on saidthird conductive layer.
 20. The method of manufacturing thesemiconductor device according to claim 16 , further comprising the stepof forming an insulating layer on said semiconductor substrate and thestep of forming a barrier layer on said insulating layer, said step offorming said conductive layer including the step of forming saidconductive layer on said barrier layer.